Rotating control device having seal responsive to outer diameter changes

ABSTRACT

A rotating control device for sealing about a drill string having a change in outer diameter can include a seal which rotates with the drill string, the seal including at least two chambers connected by a passage, and a fluid which flows between the chambers via the passage in response to displacement of the outer diameter change through the seal. A method of sealing can include forming at least two chambers in a resilient material of a seal, displacing the outer diameter change into the seal, thereby transferring fluid from a first chamber to a second chamber, and displacing the outer diameter change out of the seal, thereby transferring the fluid from the first chamber to the second chamber. One of the chambers can increase in volume while the other of the chambers decreases in volume.

TECHNICAL FIELD

This disclosure relates generally to equipment utilized and operationsperformed in conjunction with a subterranean well and, in one exampledescribed below, more particularly provides a rotating control devicewith a seal which is responsive to outer diameter changes of a drillstring.

BACKGROUND

Rotating control devices generally include one or more seals for sealingabout drill pipe while the drill pipe rotates therein. These seals canbe damaged by repeated displacement of drill pipe connections (e.g.,collars or tool joints) or other outer diameter changes through theseals. One reason is that the seals deform to allow the drill pipediameter changes to pass through them.

The seals are already compressed against the drill pipe (in order toseal), so further compression of the seals when diameter changes passthrough them further strains the seals. In addition, drill pipeconnections are typically not perfectly smooth, so the seals can also bescraped, cut, abraded, etc., when the connections pass through thealready-strained seals.

Therefore, it will be appreciated that improvements are continuallyneeded in rotating control devices and the seals therein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a representative partially cross-sectional view of a welldrilling system and associated method which can embody principles ofthis disclosure.

FIG. 2 is a representative enlarged scale partially cross-sectional viewof a rotating control device which may be used in the system and methodof FIG. 1, and which can embody the principles of this disclosure.

FIG. 3 is a representative further enlarged scale cross-sectional viewof a seal which may be used in the rotating control device of FIG. 2,and which can embody the principles of this disclosure.

FIG. 4 is a representative cross-sectional view of the seal, with anouter diameter change of a drill string being inserted into the seal.

FIG. 5 is a representative cross-sectional view of the seal, with theouter diameter change being displaced in the seal.

FIG. 6 is a representative cross-sectional view of the seal, with theouter diameter change being displaced out of the seal.

DETAILED DESCRIPTION

Representatively illustrated in FIG. 1 is a system 10 for use with asubterranean well, and an associated method, which system and method canembody principles of this disclosure. However, it should be clearlyunderstood that the system 10 and method are merely one example of anapplication of the principles of this disclosure in practice, and a widevariety of other examples are possible. Therefore, the scope of thisdisclosure is not limited at all to the details of the system 10 andmethod described herein and/or depicted in the drawings.

In the FIG. 1 example, a wellbore 12 is drilled by rotating a drill pipe14, such as, by utilizing a drilling rig (not shown) at or near theearth's surface. The drill pipe 14 can be rotated by any means, e.g., arotary table, a top drive, a positive displacement or turbine drillingmotor, etc. Thus, it should be understood that the scope of thisdisclosure is not limited to any particular way of rotating the drillpipe 14.

The drill pipe 14 is part of an overall drill string 16, which caninclude a variety of different components. Preferably, a drill bit 18 isconnected at a distal end of the drill string 16, so that the drill bitcuts into the earth when the drill string rotates and weight is appliedto the drill bit.

An annulus 20 is formed radially between the drill string 16 and thewellbore 12. A drilling fluid 22 (commonly known as “mud,” althoughother fluids, such as brine water, may be used) is circulated downwardthrough the drill string 16, exits the drill bit 18, and flows back tothe surface via the annulus 20.

The drilling fluid 22 serves several purposes, including cooling andlubricating the drill bit 18, removing cuttings, maintaining a desiredbalance of pressures between the wellbore 12 and the surrounding earth,etc. In some situations (e.g., in managed pressure drilling orunderbalanced drilling, or even in conventional overbalanced drilling),it may be desirable to seal off the annulus 20 at or near the earth'ssurface (for example, at a land or sea-based drilling rig, a subseafacility, a jack-up rig, etc.), so that communication between theannulus 20 and the earth's atmosphere or sea is prevented.

For this purpose, a rotating control device 24 can be used to seal aboutthe drill string 16 during a drilling operation. In the example depictedin FIG. 1, the rotating control device 24 is connected to a blowoutpreventer stack 26 on a wellhead 28, but in other examples the rotatingcontrol device could be positioned in or on a riser string, in a subseawellhead, in a wellbore, etc. The scope of this disclosure is notlimited to any particular location of the rotating control device 24.

Referring additionally now to FIG. 2, an enlarged scale partiallycross-sectional view of one example of the rotating control device 24 isrepresentatively illustrated. In this view, it may be clearly seen thatthe rotating control device 24 includes two annular seals 30, 32 whichseal against an exterior surface of the drill pipe 14 as the drill piperotates within an outer housing assembly 34 of the rotating controldevice. The FIG. 2 rotating control device 24 may be used with thesystem 10 and method of FIG. 1, or it may be used with other systems andmethods.

In the FIG. 2 example, the outer housing assembly 34 is provided with aflange 36 at a lower end thereof for connection to the blowout preventerstack 26. However, in other examples, the outer housing assembly 34could be provided with suitable connectors for installing the rotatingcontrol device 24 in or on a riser string, to a subsea wellhead, or atany other location.

As depicted in FIG. 2, the lower seal 30 is positioned in the outerhousing assembly 34, whereas the upper seal 32 is positioned in an upper“pot” or enclosure 38. In other examples, either or both of the seals30, 32 could be positioned inside or outside of the outer housingassembly 34, and other numbers of seals (including one) may be used. Thescope of this disclosure is not limited to any particular number orpositions of seals.

The seals 30, 32 are in one sense “passive,” in that they sealinglyengage the drill pipe 14 whenever the drill pipe is positioned in therotating control device 24, without any need of actuating the seals toeffect such sealing. However, the seals 30, 32 can also be considered“active” seals, because they are responsive to change their sealingcharacteristics when acted upon by a stimulus, as described more fullybelow.

In the FIG. 2 example, the seals 30, 32 are mounted to a bearingassembly 40, which is secured to the outer housing assembly 34 by aclamp 42. The bearing assembly 40 includes bearings 44, which permit aninner generally tubular mandrel 46 to rotate relative to the outerhousing assembly 34.

In other examples, a latch mechanism or other device could be used inplace of the clamp 42. The bearing assembly 40 and both seals 30, 32could be positioned entirely within the outer housing assembly 34. Thus,the scope of this disclosure is not limited to any particulararrangement or configuration of the various components of the rotatingcontrol device 24.

Note that, as depicted in FIG. 2, the seals 30, 32 rotate with theenclosure 38 and mandrel 46 relative to the outer housing assembly 34when the drill pipe 14 rotates in the rotating control device 24.Preferably, the drill pipe 14 is both sealingly and grippingly engagedby the seals 30, 32.

Referring additionally now to FIG. 3, the seal 30 is representativelyillustrated apart from the remainder of the rotating control device 24.The seal 30 may be used in the FIG. 2 rotating control device 24, or itmay be used in other types of rotating control devices, in keeping withthe principles of this disclosure.

In the FIG. 3 example, the drill string 16 includes an outer diameterchange 48. The outer diameter change 48 may be in the form of a tooljoint, a collar, another type of drill pipe connection, a drilling tool,etc. Any type of outer diameter change can be included in the drillstring 16, within the scope of this disclosure.

In this example, the outer diameter change 48 comprises an increasedouter diameter of the drill pipe 14. It is desired for the seal 30 tocontinue sealing against the outer diameter change 48 and the adjacentdrill pipe 14 as the outer diameter change passes through the seal,without incurring any damage to the seal, shortening its useful life,etc.

For this purpose, the seal 30 includes fluid-filled chambers 50, 52 in aresilient material 54 of the seal. The material 54 may comprise, forexample, an elastomer (such as, a nitrile, fluoro-elastomer, EPDM,etc.).

The chambers 50, 52 are preferably formed by molding them into the seal30 when the seal is fabricated. However, the scope of this disclosure isnot limited to any particular method of forming the chambers 50, 52.

An annular-shaped passage 56 connects the chambers 50, 52. The passage56 may also be formed in resilient material 54, or it may be formed in arigid or other non-resilient material if desired.

It will be appreciated that fluid 58 can flow between the chambers 50,52 via the passage 56. Thus, if one of the chambers 50, 52 is compressedor reduced in volume, the fluid 58 can flow to the other chamber via thepassage, thereby enlarging a volume of the other chamber.

The fluid 58 is preferably a compressible fluid (e.g., a liquid or gas,such as, silicone fluid, nitrogen gas, etc.). In this manner,compression of the fluid 58 will function to resiliently bias the seal30 into sealing contact with the drill pipe 14 and any outer diameterchange 48.

Referring additionally now to FIG. 4, the seal 30 is representativelyillustrated after the diameter change 48 has entered an upper portion ofthe seal. The increased outer diameter of the drill pipe 14 has caused avolume of the upper chamber 50 to decrease, thereby forcing some or allof the fluid 58 in the chamber 50 to flow via the passage 56 to theother chamber 52.

The increased volume of fluid 58 in the lower chamber 52 is beneficial,in that it causes the lower portion of the seal 30 to be increasinglybiased into sealing contact with the drill pipe 14 below the diameterchange 48. This is due in part to the volume of the lower chamber 52increasing as a result of the additional fluid 58 therein.

Referring additionally now to FIG. 5, the seal 30 is representativelyillustrated after the diameter change 48 has been displaced furtherdownward in the seal 30. The diameter change 48 in this view is nowpositioned opposite the lower chamber 52.

The lower chamber 52 is radially compressed by the presence of thediameter change 48 in the seal 30, thereby forcing the fluid 58 from thelower chamber to the upper chamber 50 via the passage 56. Thus, thevolume of the lower chamber 52 decreases, while the volume of the upperchamber 50 increases.

The increased volume of fluid 58 in the upper chamber 50 is beneficial,in that it causes the upper portion of the seal 30 to be increasinglybiased into sealing contact with the drill pipe 14 above the diameterchange 48. This is due in part to the volume of the upper chamber 50increasing as a result of the additional fluid 58 therein.

Referring additionally now to FIG. 6, the seal 30 is representativelyillustrated after the diameter change 48 has been displaced downwardlyout of the seal. The upper and lower chambers 50, 52 have now returnedto their respective FIG. 3 volumes, with some of the fluid 58 havingflowed from the upper chamber 50 back to the lower chamber 52.

The transfer of the fluid 58 between the chambers 50, 52 during thepassage of the diameter change 48 through the seal 30 allows the seal toenlarge as needed, and where needed, to prevent over-straining the seal,as well as abrasions and cuts, due to the diameter change. However,instead of decreasing the sealing capability of the seal 30, thetransfer of the fluid 58 to a particular chamber 50 or 52 allows arespective portion of the seal to be increasingly biased into sealingcontact with the drill pipe 14, thereby enhancing the sealing capabilityof the seal.

Note that these benefits can be obtained, even without applying anyexternal pressure to the chambers 50, 52. Thus, it is preferably notnecessary to connect any external pressure source (e.g., a pump, bottlesof compressed gas, etc.) to the seal 30. This simplifies theconstruction and operation of the rotating control device 24, therebyreducing manufacturing, operating and maintenance costs, while enhancingthe rotating control device's reliability and sealing capability.However, in some examples, an external pressure source could beconnected to the seal 30.

Although the diameter change 48 is depicted in FIGS. 3-6 as displacingdownwardly through the seal 30, similar benefits are obtained when thediameter change displaces upwardly through the seal. In that case, thefluid 58 would travel in opposite directions, and the chambers 50, 52would expand and contract, in reverse order to that described above forFIGS. 3-6.

Although the diameter change 48 is depicted in FIGS. 3-6 as comprising adiameter increase, similar benefits can be obtained when the diameterchange comprises a diameter decrease. In that case, the fluid 58 wouldtravel in opposite directions, and the chambers 50, 52 would expand andcontract, in reverse order to that described above for FIGS. 3-6.

The diameter change 48 could comprise a combination of diameterincreases and decreases. Thus, the scope of this disclosure is notlimited to any of the specific details of the diameter change 48, theseal 30 (or any other elements of the rotating control device 24) or themethod described above and/or depicted in the drawings.

It may now be fully appreciated that an improved rotating control device24 is provided to the art by the above disclosure. In one exampledescribed above, the rotating control device 24 seals about a drillstring 16 having a change in outer diameter 48. The rotating controldevice 24 can comprise a seal 30 which rotates with the drill string 16.The seal 30 can include at least first and second chambers 50, 52connected by at least one passage 56, and a fluid 58 which flows betweenthe first and second chambers 50, 52 via the passage 56 in response todisplacement of the outer diameter change 48 through the seal 30.

One of the first and second chambers 50, 52 can decrease in volume inresponse to an increase in volume of the other of the first and secondchambers 50, 52. Each of the first and second chambers 50, 52 mayincrease in volume and decrease in volume in response to displacement ofthe diameter change 48 through the seal 30 in any direction.

The first and second chambers 50, 52 are preferably free of anyconnection to an external pressure source. The fluid 58 may comprise acompressible fluid.

Each of the first and second chambers 50, 52 may be formed in aresilient material 54 of the seal 30, although non-resilient materialsmay be used, if desired. The passage 56 may comprise an annular spaceformed in a resilient material 54 of the seal 30. The passage 56 inother examples could be formed in a rigid or other non-resilientmaterial, and is not necessarily annular in shape (for example, holes ofvarious shapes could be used).

A method of sealing about a drill string 16 having an outer diameterchange 48 is also described above. In one example, the method comprises:forming at least first and second chambers 50, 52 in a resilientmaterial 54 of a seal 30; displacing the outer diameter change 48 intothe seal 30, thereby transferring fluid 58 from the first chamber 50 tothe second chamber 52; and displacing the outer diameter change 48 outof the seal 30, thereby transferring the fluid 58 from the first chamber50 to the second chamber 52.

Displacing the outer diameter change 48 into the seal 30 can includeflowing the fluid 58 through at least one passage 56 which connects thefirst and second chambers 50, 52, and/or increasing a volume of thesecond chamber 52. Displacing the outer diameter change 48 into the seal30 may be performed without either of the first and second chambers 50,52 being connected to an external pressure source.

The method can include forming the passage 56 in the resilient material54.

Displacing the outer diameter change 48 out of the seal 30 can includeflowing the fluid 58 from the second chamber 52 to the first chamber 50via the passage 56, and/or increasing a volume of the first chamber 50.

The passage 56 can comprise an annular space.

The method can include displacing the outer diameter change 48 withinthe seal 30, thereby displacing the fluid 58 from the second chamber 52to the first chamber 50.

Also described above is a seal 30 for sealing about a drill string 16 ina rotating control device 24, the drill string 16 having an outerdiameter change 48. In one example, the seal 30 can include at leastfirst and second chambers 50, 52. One of the first and second chambers50, 52 increases in volume while the other of the first and secondchambers 50, 52 decreases in volume.

The first one of the first and second chambers 50, 52 decreases involume in response to an increase in volume of the other of the firstand second chambers 50, 52.

Each of the first and second chambers 50, 52 increases in volume anddecreases in volume in response to displacement of the outer diameterchange 48 through the seal 30. This displacement may be in anydirection. The diameter change 48 may be an increase and/or a decreasein diameter.

The first and second chambers 50, 52 may be free of any connection to anexternal pressure source. Each of the first and second chambers 50, 52may be formed in a resilient material 54 of the seal 30.

The first and second chambers 50, 52 are preferably connected by atleast one passage 56. The passage 56 may comprise an annular spaceformed in a resilient material 54 of the seal 30.

The seal 30 can include a fluid 58 which flows between the first andsecond chambers 50, 52 via the passage 56 in response to displacement ofthe diameter change 48 through the seal 30. The fluid 58 may comprise acompressible fluid, although compressible fluid(s) may be used inaddition to, or in place of, compressible fluid.

Although various examples have been described above, with each examplehaving certain features, it should be understood that it is notnecessary for a particular feature of one example to be used exclusivelywith that example. Instead, any of the features described above and/ordepicted in the drawings can be combined with any of the examples, inaddition to or in substitution for any of the other features of thoseexamples. One example's features are not mutually exclusive to anotherexample's features. Instead, the scope of this disclosure encompassesany combination of any of the features.

Although each example described above includes a certain combination offeatures, it should be understood that it is not necessary for allfeatures of an example to be used. Instead, any of the featuresdescribed above can be used, without any other particular feature orfeatures also being used.

It should be understood that the various embodiments described hereinmay be utilized in various orientations, such as inclined, inverted,horizontal, vertical, etc., and in various configurations, withoutdeparting from the principles of this disclosure. The embodiments aredescribed merely as examples of useful applications of the principles ofthe disclosure, which is not limited to any specific details of theseembodiments.

In the above description of the representative examples, directionalterms (such as “above,” “below,” “upper,” “lower,” etc.) are used forconvenience in referring to the accompanying drawings. However, itshould be clearly understood that the scope of this disclosure is notlimited to any particular directions described herein.

The terms “including,” “includes,” “comprising,” “comprises,” andsimilar terms are used in a non-limiting sense in this specification.For example, if a system, method, apparatus, device, etc., is describedas “including” a certain feature or element, the system, method,apparatus, device, etc., can include that feature or element, and canalso include other features or elements. Similarly, the term “comprises”is considered to mean “comprises, but is not limited to.”

Of course, a person skilled in the art would, upon a carefulconsideration of the above description of representative embodiments ofthe disclosure, readily appreciate that many modifications, additions,substitutions, deletions, and other changes may be made to the specificembodiments, and such changes are contemplated by the principles of thisdisclosure. For example, structures disclosed as being separately formedcan, in other examples, be integrally formed and vice versa.Accordingly, the foregoing detailed description is to be clearlyunderstood as being given by way of illustration and example only, thespirit and scope of the invention being limited solely by the appendedclaims and their equivalents.

What is claimed is:
 1. A rotating control device for sealing about adrill string having a change in outer diameter, the rotating controldevice comprising: a seal which rotates with the drill string, the sealincluding at least first and second chambers connected by at least onepassage, and a fluid which flows between the first and second chambersvia the passage in response to displacement of the outer diameter changethrough the seal.
 2. The rotating control device of claim 1, wherein oneof the first and second chambers decreases in volume in response to anincrease in volume of the other of the first and second chambers.
 3. Therotating control device of claim 1, wherein each of the first and secondchambers increases in volume and decreases in volume in response todisplacement of the diameter change through the seal.
 4. The rotatingcontrol device of claim 1, wherein the first and second chambers arefree of any connection to an external pressure source.
 5. The rotatingcontrol device of claim 1, wherein the fluid comprises a compressiblefluid.
 6. The rotating control device of claim 1, wherein each of thefirst and second chambers is formed in a resilient material of the seal.7. The rotating control device of claim 1, wherein the passage comprisesan annular space formed in a resilient material of the seal.
 8. A methodof sealing about a drill string having an outer diameter change, themethod comprising: forming at least first and second chambers in aresilient material of a seal; displacing the outer diameter change intothe seal, thereby transferring fluid from the first chamber to thesecond chamber; and displacing the outer diameter change out of theseal, thereby transferring the fluid from the first chamber to thesecond chamber.
 9. The method of claim 8, wherein displacing the outerdiameter change into the seal further comprises flowing the fluidthrough at least one passage which connects the first and secondchambers.
 10. The method of claim 9, further comprising forming thepassage in the resilient material.
 11. The method of claim 9, whereindisplacing the outer diameter change out of the seal further comprisesflowing the fluid from the second chamber to the first chamber via thepassage.
 12. The method of claim 9, wherein the passage comprises anannular space.
 13. The method of claim 8, wherein displacing the outerdiameter change into the seal further comprises increasing a volume ofthe second chamber.
 14. The method of claim 13, wherein displacing theouter diameter change out of the seal further comprises increasing avolume of the first chamber.
 15. The method of claim 8, whereindisplacing the outer diameter change into the seal is performed withouteither of the first and second chambers being connected to an externalpressure source.
 16. The method of claim 8, further comprisingdisplacing the outer diameter change within the seal, thereby displacingthe fluid from the second chamber to the first chamber.
 17. A seal forsealing about a drill string in a rotating control device, the drillstring having an outer diameter change, the seal comprising: at leastfirst and second chambers, and wherein one of the first and secondchambers increases in volume while the other of the first and secondchambers decreases in volume.
 18. The seal of claim 17, wherein the oneof the first and second chambers decreases in volume in response to anincrease in volume of the other of the first and second chambers. 19.The seal of claim 17, wherein each of the first and second chambersincreases in volume and decreases in volume in response to displacementof the outer diameter change through the seal.
 20. The seal of claim 17,wherein the first and second chambers are free of any connection to anexternal pressure source.
 21. The seal of claim 17, wherein each of thefirst and second chambers is formed in a resilient material of the seal.22. The seal of claim 17, wherein the first and second chambers areconnected by at least one passage.
 23. The seal of claim 22, wherein thepassage comprises an annular space formed in a resilient material of theseal.
 24. The seal of claim 22, further comprising a fluid which flowsbetween the first and second chambers via the passage in response todisplacement of the diameter change through the seal.
 25. The seal ofclaim 24, wherein the fluid comprises a compressible fluid.